The present invention generally relates to semiconductor devices and more particularly to the fabrication of a high-speed semiconductor device having a silicide film.
The technology of self-aligned silicide (salicide) is a technology of forming a low-resistance silicide layer on the surface of a diffusion region formed on a silicon substrate or on the surface of a polysilicon gate electrode. The salicide process is an indispensable technology in the fabrication of modern high-speed semiconductor devices including logic devices and memory devices.
In salicide technology, a metal film of Co or Ni is deposited on a silicon substrate so as to cover the diffusion region or the polysilicon gate electrode, and a reaction process is conducted thereafter for causing the metal film to react with the surface of the diffusion region or the surface of the polysilicon gate electrode. As a result, there is formed an extremely thin silicide film on the surface of the diffusion region or the surface of the polysilicon gate electrode.
In conventional high-speed semiconductor devices, titanium silicide has been used extensively for such a silicide film, while in recent, ultrahigh-speed semiconductor devices having the gate length of 90 nm or less, cobalt silicide or nickel silicide is used commonly in view of the possibility of reducing the thermal annealing temperature at the time of the silicide formation reaction.
With such salicide technology, it has been generally thought important to remove impurity, particularly native oxide film, from the surface of the diffusion region or from the surface of the polysilicon gate electrode prior to the deposition of the metal film.
(Patent Reference 1) Japanese Laid-Open Patent Application 2002-334850